Co-localization of glucocorticoid metabolizing and prostaglandin synthesizing enzymes in rat kidney and liver.
OBJECTIVE
The kidney metabolizes endogenous glucocorticoids using one of 2 isoforms of the enzyme 11ss-Hydroxysteroid Dehydrogenase (11ss-HSD). 11ss-HSD1 is located in the later portion of the proximal tubule and interstitial cells and 11ss-HSD2 is found in the mineralocorticoid sensitive collecting duct. Both renal isoforms appear to function as dehydrogenases, inactivating glucocorticoids. Since our laboratory has established that both renal cyclo-oxygenase-2 (COX-2) and 11ss-HSD1 co-localize in human kidney, we hypothesized that the two enzymes might functionally interact and influence each other's expression and/or activity.


RESULTS
Using immuno-histochemistry staining with specific antibodies, both enzymes co-localize in later segments of proximal tubules in rat kidney and in rat hepatocytes. There was no co-localization with 11ss-HSD2 in the kidney. The co-localization was confirmed by Western blot and by immuno-precipitation in cultured rat proximal tubular cells (IRPTC). IRPTC incubated with corticosterone 1 microM or with corticosterone 10 nM plus the 11ss-HSD inhibitor carbenoxolone 1 microM demonstrated a decrease in the expression of COX-2 by Western blot at 24 h. When IRPTC were exposed to the COX-2 inhibitor, celecoxib, 11ss-HSD1 dehydrogenase activity was inhibited in a dose dependent manner with an IC50 of 1.4 microM. Celecoxib 2 microM had minimal effect on reductase activity in liver slices.


CONCLUSIONS
Thus, COX-2 and 11ss-HSD1 co-localize in renal proximal tubules and in hepatocytes. In the kidney, each can influence the biological function of the other. The NSAID celecoxib may exert some of its anti-inflammatory effects on the kidney by locally prolonging the biologic half-life of endogenous glucocorticoids.
Gong
Rujun
R
Division of Kidney Diseases and Hypertension Rhode Island Hospital, Providence RI, United States.
Latif
Syed
S
Morris
David J
DJ
Brem
Andrew S
AS
D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000378:metabolism; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2 / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D051546:Cyclooxygenase 2 / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005938:Glucocorticoids / Q000096:biosynthesis*; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000201:enzymology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D011453:Prostaglandins / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013256:Steroids / Q000096:biosynthesis
D005938:Glucocorticoids; D007527:Isoenzymes; D011453:Prostaglandins; D013256:Steroids; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2; D051546:Cyclooxygenase 2